Perl is written in C. All of the operators ("core functions") are implemented in C.

It was said that glob was written in Perl, but it's pp_glob in pp_sys.c. (*Sometimes*, this does result in Perl getting executed, but not always.)

It was said that dbmopen was written in Perl, but it's pp_dbmopen in pp_sys.c. (Granted, this does result in Perl code getting executed.)

There are many core and non-core modules written in Perl, but the functions in perlfunc are necessarily written in C.